The present invention relates to a lancet system in the form of a lancet magazine which can be used in a lancing aid for collecting blood for diagnostic purposes.
In a variety of diseases it is necessary to examine human blood for an analyte contained therein. In many cases this only requires the withdrawal of a small amount of blood from the body in the form of a blood drop by producing a small puncture wound. A particularly important example of such a case is diabetes in which the glucose content of blood has to be examined at regular intervals. Blood may also for example be examined with regard to coagulation parameters, triglycerides, HbA1c or lactate. Blood lancet devices which consist of a lancing device and tailor-made replaceable lancets are usually used to produce the required puncture wounds. A lancet holder in which one interchangeable lancet can be inserted is present in the housing of the lancing device. During the lancing operation the lancet holder is rapidly moved in a lancing direction by a lancet drive which is also integrated into the lancing device until the lancet tip emerges from an exit opening provided at the front end of the lancing device and produces a small puncture wound in the part of the body that is pressed against the front end. Afterwards the lancet holder containing the lancet is moved back in the opposite direction to the lancing.
Small, easy to handle blood collection devices, so-called lancing aids that can be easily and reliably operated by the user and enable a part of the body to be lanced in a manner that is as pain-free as possible are now routinely used. In order to avoid infections especially in hospitals, the lancets are disposable elements intended for single use. After a lancet has been used once, the lancet is removed after the lancing operation or ejected from the device and discarded as refuse. In such a case the exposed lancets in a refuse container may lead to injury during waste disposal which may result in a contamination of other persons by the used lancet. Such contamination may lead to infections and thus some countries are planning to impose a ban on blood collection systems in which the needle tip is freely accessible after use. In addition to a risk of injury during waste disposal, there is also a risk that a used lancet may be accidentally re-used. This is particularly relevant for hospitals in which a lancing aid is used for several patients since such inadvertence of the nursing staff could lead to a patient being contaminated with the blood of a previous patient.
In addition to the use of blood lancet devices by medical staff, lancing aids are also used by laymen in the so-called home-monitoring field. This is particularly the case for monitoring the treatment of diabetics. Thus, it has been found in the treatment of diabetics that serious damage associated with diabetes such as loss of sight can be substantially reduced when the glucose concentration in the blood of the diabetic is determined frequently and up to five times daily and the insulin injection is exactly adjusted on the basis of these measurements. Lancing aids which enable the diabetic to carry out such a blood examination by himself are used for home-monitoring in order to carry out such frequent measurements. The resulting requirements for a blood lancet device are a simple handling when inserting new lancets and a reliable ejection of used lancets in addition to a simple handling when triggering the lancing operation and a relatively painless puncture. Lancet replacement should on the one hand be as simple as possible and, on the other and, ensure the utmost safety with regard to unintentional injury of the user or other persons. Although in the home-monitoring field it is conceivable that a lancet, once inserted, is used several times for lancing by the same user, even in this case an accidental re-use of an ejected lancet should be prevented once the user has decided to discard the lancet. Furthermore, other persons in particular should be reliably protected from the discarded lancets for example during waste disposal.
In the prior art the tip of the lancet is usually surrounded by a tip cover made of plastic when the lancet is inserted which allows a safe handling when the lancet is inserted. When the lancet is inserted, the tip cover is removed to expose the sharp tip of the lancet for the lancing operation. See, e.g., U.S. Pat. No. 5,628,765. However, due to the exposed lancet tip there is a risk of accidental injury and the tip may become damaged. The lancet is removed from the lancing aid after one or several lancing operations. This can either be carried out manually in which case there is a high risk of injury by the lancet tip or by an automatic ejection mechanism.
A blood lancet device is disclosed in EP 0 565 970 in which the lancet is ejected from the lancet holder by means of an ejecting rod. The user can operate the ejecting rod by pressing a corresponding button.
Furthermore, an ejecting mechanism is described in the patent document U.S. Pat. No. 4,442,836 where the lancet is automatically released when the lancing aid is retensioned so that the used lancet is discarded after each lancing operation. Such ejecting mechanisms require a relatively high degree of additional engineering. Moreover, multiple use of an already inserted lancet system is not possible, which is, however, often desired by customers especially in the home-monitoring field. Another major disadvantage of the described prior art is that the lancet tip is unprotected after the lancet has been ejected resulting in an associated risk of injury as described above.
In order to facilitate the safe removal of a used lancet, blood collection systems are also described in the prior art which ensure that the lancet tip is protected after ejecting the lancet. This is regarded as an essential feature especially for elderly users or those who are handicapped by poor sight and shaky or trembling hands as a result of disease.
A protection of the lancet tip is achieved in the prior art by integrating the lancet in a cap of the lancing aid such that the lancet and the housing cap together form a replaceable disposable unit. Such designs are described in the documents EP 0 595 148 and U.S. Pat. No. 4,990,154, U.S. Pat. No. 5,454,828 and U.S. Pub. No. 2004-0034318. When the lancet is ejected by the user, the housing cap is placed over the lancet tip so that the lancet surrounded by the cap can be subsequently discarded. Even if the lancet tip is protected after ejection by the described mechanism, it is nevertheless possible for a careless user to reinsert a lancet that has already been ejected once and carry out a new lancing operation. Consequently the user himself has to recognize that the lancet has already been used.
The document EP 0 630 609 discloses a mechanism which directly prevents reinsertion and thus re-use of a lancet that has been ejected once. The described lancet device comprises a lancet with a lancet body which breaks when the lancet is ejected from the lancing aid to prevent a reinsertion of the lancet. This prevents the user from re-using a contaminated lancet. However, a disadvantage of the prior art is that the lancet tip is unprotected after the lancet has been ejected.
For individual lancets there are a wide variety of solutions for protecting a user from the used lancet tip. Thus, various mechanisms are described in the documents U.S. Pat. No. 5,964,731, U.S. Pat. No. 7,001,364 and U.S. Pat. No. 5,454,828 relating to how a protecting mechanism can be brought over the lancet after use so that the lancet cannot be re-used. However, these mechanisms either have to be applied by the user himself which limits the effectiveness of the protection from injury or the mechanism is automatically triggered after each lancing operation by the lancing mechanism of the lancing aid as described in WO 2008/072414 so that the lancet can only be used once in an inserted state.
A protection against re-use is described in U.S. Pat. No. 7,785,338 which enables the housing of the lancet system to be changed after use of a lancet system in such a manner that it can no longer interact in a regular manner with a lancing aid. This is achieved by a change in the coupling site between the lancet magazine and lancing aid. In this case it is no longer possible to reinsert an already used magazine. This is intended to protect the user against re-using an already used lancet. However, a disadvantage of this prior art is that the coupling site of the lancing aid can be damaged when it is attempted to reinsert an already used magazine into the lancing aid if the user does not immediately recognize that the magazine no longer correctly fits the coupling site of the lancing aid.